vacuum tube with linear dynamic



Ma 1964 P. K. GEORGIES VACUUM TUBE WITH LINEAR DYNAMIC CHARACTERISTICS Filed Dec. 11, 1961 INVENTOR.

Philip K. Georgies W ATTORNEY United States Patent 0.

3,125,699 VACUUM TUBE WITH LINEAR DYNAMIC CHARACTERISTICS Philip K. Georgies, 32.02 8th St. NE, Washington 17, D.C. Filed Dec. 11, 1961, Ser. No. 158,426 3 Claims. (Cl. 313-299) This invention relates to vacuum tubes intended to control, modify, or amplify current flow therethrough in accordance with the application of control potential to a grid element, and has for its primary object the provision of a vacuum tube having a linear dynamic characteristic over an extended range.

Known types of vacuum tubes employ primarily two techniques for controlling the current flow therethrough; one is the familiar grid technique employed in all present triodes and pentodes, and the other method is the deflection technique. The grid technique, in which the input voltage is applied to a control grid, results in a nonlinear dynamic characteristic when the range of the control voltage is extended, which produces a large amount of distortion in the output when the tube is used as an amplifier. The deflection technique can give linear dynamic characteristics, but only very small currents can be controlled, and very high voltages are required, which is a serious limitation in most practical cases.

According to the invention, both of the above techniques are combined in a special electrode design. The grid control is employed as the major control factor, and the deflection technique is also employed to exert a partial control only to the extent required to correct for the distortion eifect of the grid control so as to produce a linear dynamic characteristic over an extended range. Since the deflection technique is not employed for the full control, it is not necessary to use very high voltages as in the case where the deflection technique is entirely relied upon for control.

It is therefore a major object of the invention to provide a vacuum tube having substantially the dimensions, operating voltages, and cost of a conventional grid-controlled tube but utilizing beam-deflection techniques to eliminate a large part of the distortion ordinarily encountered in grid-control tubes.

A further object is to provide such a tube which lends itself readily to present mass-production techniques, which is rugged in construction, and which can easily be manufactured in various tube types having tube characteristics corresponding to presently employed tube types.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawing, in which:

FIG. 1 is a side view of a vacuum tube to which the invention is applied;

FIG. 2 is a sectional View taken on line 2-2 of FIG. 1;

FIG. 3 is a view similar to FIG. 2, but showing the elements in perspective;

FIG. 4 is a schematic tube circuit diagram showing the arrangement and interconnection of the elements;

FIG. 5 is a perspective view of portions of the main and secondary plates;

FIG. 6 is a typical circuit diagram in which the tube may be utilized; and

FIG. 7 shows characteristic curves of a typical tube according to the invention, showing the principle of operation.

Referring to FIG. 1, the vacuum tube of the invention may be of conventional external appearance, embodying an envelope 2, a base 3, and pins 4 for connection to a conventional tube socket. The electrode structure to be described is supported in conventional fashion between 3,125,699 Patented Mar. 17, 1964 "ice v upper and lower plates 6 and 7 respectively, of insulating material.

Referring to FIGS. 2 and 3, the tube has a conventional cathode 8, which may be of any conventional construction such as is commonly employed in beam power tubes. The control grid 9, also of conventional construction, is wound in a generally helical fashion about supporting posts 10 and 11, which extend between plates 6 and 7, and are supported thereby. The screen grid 12, also of conventional construction, is similarly supported on posts 13 and 14. Deflection electrode 16 has the same structure as the usual beam-confining plate in a commercial beam power tube but has a different function, as will be explained below. Electrode 16 is connected to the control grid, as shown in FIG. 4. Electrode 16 is provided with four fins 17 added at the edges and positioned to face beam divider electrodes 18. Electrodes 18 are connected to the cathode as shown in FIG. 4, and function to split the electron beam into two separate beams of electrons, since, being at the same potential as the cathodes, they act to repel or deflect away electrons coming toward them.

Electrode 19 is the main plate or anode, and has the special design shown in FIG. 5. It will be noted that in the path of the beam, the electrode has been cut away as shown at 21 so as to intercept more or less of the electrons from the cathode, in accordance with the lateral position of the beam, which position is in turn determined by the control potentials and particularly by the control grid potential since deflection electrode 16 is connected to the control grid. Those electrons which are not intercepted by the main plate 19 pass through the aperture 21 and impinge upon secondary plate 22 which is spaced from the opposing surface of electrode 19, and is separately connected to one of the external pins 4 (FIG. 1) of the tube.

Referring to FIG. 6, it will be seen that the secondary electrode 22 is connected through an individual resistor 28 to the B+ side of the plate power supply. The effective signal is taken through a conventional load resistor 24 connected to the main plate 19, and may be supplied to the utilization device through a conventional coupling capacitor 26.

Present commercial pentodes have the dynamic characteristics shown in curve A of FIG. 7. The departure from linearity of this curve over its main working portion represents distortion, which is either put up with, or else various circuit expedients are utilized to minimize it, requiring additional circuit components or more complex circuitry, and in some cases elaborate compensating circuitry is resorted to in order to achieve as low distortion as possible. In the present design, as the control voltage applied to the grid becomes more negative a larger and larger percentage of the electrons in the beam pass through the aperture 21 and reach the secondary plate 22. The resulting current in the secondary plate is shown at curve C, and is in effect subtracted from curve A, leaving the current characteristic of the main plate substantially linear over the entire useful range, as shown by curve B. It will be apparent that the shape of curve C can be controlled by properly adjusting the shape of the orifice 21, so that it subtracts the proper number of electrons from the beam to leave the resulting main plate current in the desired linear configuration.

At high plate current, both electrodes 17 and 18 are about at the same potential; therefore, most of the space current will be collected at the main plate. When the grid voltage, and with it the voltage of electrode 16, increases in the negative direction, divider electrode 18 will be at a positive potential relative to electrode 16; there fore, both electron beams will be deflected more toward the center of the main path. The aperture in the main plate is so designed that the area of the opening in line with the beam increases as the electron beams move toward the center of the plate. Therefore, at a low level of space current, larger amounts of electrons will leak through the window of the main plate and be collected by the secondary plate 22. Actually, there are four electron beams in the structure shown, since it is symmetrical both laterally and longitudinally. Since all of these beams move symmetrically, it is necessary to consider only the action of a single one of these four beams. The abovedescribed operation obviously accounts for the shape of curve C in FIG. 7. could be made as a single-beam or double-beam structure, but the four-beam structure shown is eflicient and conforms to standard tube construction and dimensions.

The operation above described has the characteristic that the larger amount of deflection is required at low space current, which makes it possible to control amount of current by deflection technique, without requiring the use of excessively high voltages. The result of current division between the two plates is a linear cynamic char-' acteristic for the main plate current, as'shown in FIG. 7. The current collected by the secondary plate 22 is not utilized at all, since it is fundamentally the distortion current in present commercial vacuum tube pentodes. The effective signal is taken across a separate load resistor 24 so that it is not influenced by this distortion current. The bias and operating voltages, asshown in FIG. 6, are within the low voltage range of present commercial receiving and amplifying tubes. applied to larger transmitting tubes operating at higher voltages.

It will be apparent that the embodiments shown are only exemplary and that various modifications can be made in construction and arrangement within the scope of my invention as defined in the appended claims.

I claim:

1. A vacuum tube having a central cathode; at least one control grid surrounding said cathode and adjacent" it; a screen grid surrounding said control grid; a beam confining plate surrounding and electrcially connected to said control grid; said beam confining plate having two It will be apparent that the tube However, the principle can also be beam apertures respectively on diametrically opposite sides of said cathode; a beam dividing electrode centrally located in each of said bearn apertures and electrically connected to said cathode; main plate means located beyond said beam confining plate and said beam dividing electrode in the beam path of said beam apertures, said main plate means having apertures also in the path of said beam apertures, said main plate apertures being shaped to pass a varying portion of an electron beam emerging through said beam apertures as the electron beam is deflected; and secondary plate means located beyond and in line with the main plate apertures for disposing of said portions of the beam passing through said main plate apertures.

2. The invention according to claim 1, said main plate apertures being shaped to pass that portion of an electron beam corresponding to the distortion component of the grid-voltage, plate-current characteristic.

3. A vacuum tube having a central cathode, at least one control grid surrounding said cathode and adjacent it; a screen grid surrounding said control grid; a beam confining plate surrounding and electrically connected to said control grid; said beam confining plate having a beam aperture on one side of said cathode; a beam dividing electrode centrally located in said beam aperture and electrically connected to said cathode; main plate means located beyond said' beam confining plate and said beam dividing electrode in the beam path of said beam aperture; said main plate means having an aperture also in the path of said beam aperture; said main plate aperture being shaped to pass a varying portion of an electron beam emerging through said beam aperture'as the electron beam is deflected; and secondary plate means located beyond and in line with the main plate aperture for disposing of said portion of the beam passing through said main plate aperture.

2,716,204 Rodenhuis Aug. 23, 1955 Van Overbeek et al. July 10, 1956 

1. A VACUUM TUBE HAVING A CENTRAL CATHODE; AT LEAST ONE CONTROL GRID SURROUNDING SAID CATHODE AND ADJACENT IT; A SCREEN GRID SURROUNDING SAID CONTROL GRID; A BEAM CONFINING PLATE SURROUNDING AND ELECTRICALLY CONNECTED TO SAID CONTROL GRID; SAID BEAM CONFINING PLATE HAVING TWO BEAM APERTURES RESPECTIVELY ON DIAMETRICALLY OPPOSITE SIDES OF SAID CATHODE; A BEAM DIVIDING ELECTRODE CENTRALLY LOCATED IN EACH OF SAID BEAM APERTURES AND ELECTRICALLY CONNECTED TO SAID CATHODE; MAIN PLATE MEANS LOCATED BEYOND SAID BEAM CONFINING PLATE AND SAID BEAM DIVIDING ELECTRODE IN THE BEAM PATH OF SAID BEAM APERTURES, SAID MAIN PLATE MEANS HAVING APERTURES ALSO IN THE PATH OF SAID BEAM APERTURES, SAID MAIN PLATE APERTURES BEING SHAPED TO PASS A VARYING PORTION OF AN ELECTRON BEAM EMERGING THROUGH SAID BEAM APERTURES AS THE ELECTRON BEAM IS DEFLECTED; AND SECONDARY PLATE MEANS LOCATED BEYOND AND IN LINE WITH THE MAIN PLATE APERTURES FOR DISPOSING OF SAID PORTIONS OF THE BEAM PASSING THROUGH SAID MAIN PLATE APERTURES. 